The embattled Mexican border city of Ciudad Juarez had its bloodiest year ever with 3,111 people killed in drug violence, an official said.

The city across the frontier from El Paso, Texas, has seen its homicide rate soar to one of the highest in the world since vicious turf battles broke out between gangs representing the Juarez and Sinaloa cartels in 2008.

That year, 1,587 people were killed in drug violence, and the toll increased to 2,643 in 2009.

Ciudad Juarez's bloodiest month last year was October, when 359 people were killed, said Arturo Sandoval, a spokesman for prosecutors in Chihuahua state, where the city is located.

Mr Sandoval did not give statistics on murders unrelated to the drug war.

More than 30,000 people have been killed in drug violence nationwide since President Felipe Calderon launched an offensive against the cartels after taking office in December 2006.

In the southern state of Guerrero, four members of a family were killed when gunmen opened fire at a New Year's celebration in the town of Piedra Iman.

State investigators said the four men, ages 80, 60, 32 and 17, were killed at a party on a basketball court.